What happens if an employer treats part-time workers less favourably than comparable full-time workers?

Part-time workers who consider that they have been treated less favourably, in breach of their statutory rights under the Part-time Workers (Prevention of Less Favourable Treatment) Regulations 2000 (SI 2000/1551), may request a written statement from their employer explaining the reasons for any less favourable treatment. The employer must comply with such a request within 21 days. The contents of the written reply, or the fact of the employer's failure to provide a statement, are admissible in evidence before an employment tribunal.